The aim of the project is to localize specfici mRNA for neural adhesion molecules to dendritic shafts and spines in hippocampi of rats or mice by in situ hybridization the the electron microscopic level under conditions where synaptic plasticity is enhanced, e.g. after induction of long term portentiation and learning. The use of IVEM should greatly aid these experiments because more mRNA molecules are contained within thick sections so there is a greater probability of observing a signal in a given section. These experiments are motivated by findings showing that synaptic plasticity changes adhesion molecule expression and that perturbation of adhesion molecule function alters plasticity in some synapses but not others.